The invention concerns a housing for an electrical device, in particular an electronic open-loop or closed-loop device for an electromechanical system according to the preamble of the main claim.
In the production of such housings for an electrical device, in particular for the open-loop control of electromechanical systems, e.g., in a motor vehicle, it must be ensured that a tight connection of the housing parts as well as good electromagnetic shielding (EMC) for the control-unit electronics can be achieved with the lowest possible production expense.
An electrical device is already known from DE-OS 39 37 190, in the case of which the control-unit electronics for components of an internal combustion engine are located in a housing that is installed in the region of the engine assemblies. The double-component housing made of metal can be closed in an electromagnetically-shielded fashion, whereby a connection device for connecting lines is integrated in the housing, via which said connecting lines the power supply and the transmission of measurement and control signals are possible.
A multiple-component housing for electronic control units is made known in DE 42 43 180 A1, in the case of which a printed-circuit board carrying the power components and the control components is provided with a circumferential covering made of electrically and thermally conductive material in order to obtain sufficient interference radiation density and good heat dissipation. The printed-circuit board is clamped here between the housing halves in the region of these coverings, which are interconnected in electrically conductive fashion, whereby the power components are contacted in thermally conductive fashion with this covering. Control elements having intensive interference radiation or that are sensitive to interference radiation are enclosed by connecting pieces projecting out of the wall of the housing parts.
It is further known that, in the case of some control-unit housings, the opening for the plug connector in the connection device of the housing is shielded against high-frequency interference radiation by the installation of a grounded metallic screen. Despite the use of non-conductive materials for the plug connection insulator, a Faraday cage is therefore approximately produced, by means of which undesired incident radiation as well as radiation can be effectively suppressed. The contacting of these grounded metallic screens to the control-unit ground requires geometries, however, that make it very difficult to seal the housings. The mechanical stiffness of the housing in the region of the plug-connection opening must be ensured by increasing the thickness of the surrounding walls of the housing.
The housing described initially having at least two housing parts and a printed-circuit board capable of being attached in the housing, as well as a connection device capable of being attached to the housing, is further developed, according to the invention, with the characterizing features of claim 1. According to the invention, a housing wall integrally joined with a housing part is advantageously provided, with which said housing wallxe2x80x94after the housing parts are joinedxe2x80x94an interference radiation-proof chamber for accommodating the connection device is formed for tight as well as untight devices.
The mechanical stiffening of the housing obtained with the housing wall according to the invention also makes it possible to optimize the thickness of the surrounding housing walls. The plug-connection opening that is closed by means of the housing wall according to the invention then no longer needs to be stabilized by mechanically strengthening the surrounding walls.
The housing according to the invention preferably has at least one electrically conductive contact element between the housing wall of the chamber and conductor tracks of the printed-circuit board interconnected with a ground connection of the housing. By using the housing wall in conjunction with the contact element or contact elements, mechanically untight as well as tight devices can also be easily equipped with a high frequency-proof cage, independent of the shape of the plug connector in the connection device, in particular for use with an open-loop and/or closed-loop control system for an electromechanical component in a motor vehicle. Frequencies in the GHz rangexe2x80x94as used in mobile radiocommunications, for examplexe2x80x94having wavelengths smaller than 50 cm are to be taken into consideration in particular. A sufficient level of electromagnetic shielding is not ensured unless openings and, in particular, gaps, are markedly smaller than the wavelengths of the incident interference radiation. The linear dimension of gaps is to be taken into consideration in particular as well. The advantageous design of the housing wall including a contact element now makes it possible to conduct the electromagnetic radiation in the region of the contact element toward the housing ground and therefore reduce the effective gap length. By attaching a plurality of contact elements, the gap lengths are further reduced and the electromagnetic compatiblity is therefore improved toward higher frequencies.
A contact element can also be advantageously provided between the cover and the printed-circuit board. As a result, an electromagnetically-protected region is also formed on the top side of the printed-circuit board, and attachment of components in this region is also made possible.
Flexible spring elements can be used advantageously as contact elements. They make easy and rapid assembly possible, and small changes in the gap height can be compensated.
Furthermore, projections can be advantageously provided on the housing wall and/or the cover, so that electrical contacting can take place without further contact elements or using simple contact elements.
In a further embodiment, the projections can serve as receptacles for contact elements, in particular contact springs. As a result, the advantages of a mechanically stable projection and a contact element can be combined with each other. The gap height is therefore essentially bridged by the projections, and the contacting takes place via a flexible contact element, for example.
The gap heights can be advantageously selected in such a fashion that components are located in the gap region. This allows for greater freedom in terms of circuit design.
Capacitors are advantageously situated in the gap region that can decouple interferences from outside the electromagnetically protected region.
Advantageously, the housing wall is integrally joined with the housing part. The housing wall can be produced at the same time as the housing part in a single step in a die-casting procedure, for example. The integral attachment of the housing wall stiffens the housing wall while making it possible to reduce the thickness of the housing walls without sacrificing stability.
Advantageously, the housing is developed in die-cast aluminum. This makes it possible to easily produce a stable, conductive housing with good thermal conduction properties.
These and further features of preferred further developments of the invention arise not only from the claims, including the backwardly referenced dependent claims, but from the description and the drawings as well, whereby each of the individual features can be realized individually or in plurality in the form of subcombinations in the case of the exemplary embodiment of the invention and in other fields, and they can represent advantageous embodiments that are themselves patentable, for which said embodiments protection is claimed here.